D.G.
From what you described, my almost 4 year old son exhibits the same behaviors but maybe to a lesser intensity (I'm a stay at home mom who used to be a teacher). We just added baby #2 to the mix 6 months ago too. What I can tell you is that in do time, hopefully with the help of the teacher and your consistent expectations, limits and consequences at home, the behaviors will lessen until the extinguish. One thing I started doing with my son is involving him in other activities outside the home that I was present for (i.e. library time, music, gymnastics, swimming). This way, he was responsible for following someone else's rules/structure/etc. but when he was disruptive I could intervene. He had always been good for me and respected my authority, so when I had to intervene it helped. His preschool teacher says that his behavior is much better on the days when I volunteer to help in the class. I guess my presence helps keep him in check. While I know this is very difficult, please remember that she is only 4 and this will not be her behavior forever. Maybe you and the teacher can pick several behaviors (1-3) to work on. The teacher can give her 3 warning and then a strike if she does not comply. If she has a good day the teacher can give her a sticker (you can help out by supplying them). Then, you can reinforce her good day/bad days at home with something as well. It sounds as though she may be bright. If you know that she responds to you telling her things you can get books from the library about these behaviors and read them to her. You can then role play these things at home. Lastly, my son and I "talk" about the expectations of his behavior on his way to school.
Sorry to be so wordy... hope some of these suggestions help. And just remember, you're a great mom, you have a great child and this is just a tiny blip on the radar.